This invention relates to catalysts for removing sulfur compounds from industrial gases, to a process for the production of these catalysts and to their use for removing sulfur compounds from industrial gases.
Sulfur-containing compounds, such as carbon oxysulfide, carbon disulfide and hydrogen sulfide, are frequent impurities in industrial gases such as carbon monoxide, carbon dioxide, nitrogen, methane and natural gas. The sulfur-containing compounds are formed, for example, during the processing of sulfur-containing gaseous, liquid or solid starting materials, such as natural gas, petroleum, coke and coal.
In many cases, these sulfur-containing constituents have to be removed from industrial gases to prevent catalyst damage, corrosion, unwanted secondary reactions in organic and inorganic synthesis. Removal is also necessary in view of the high toxicity of the sulfur-containing compounds, even in low concentrations.
Hydrogen sulfide, the most common companion of carbon oxysulfide and carbon disulfide, can be removed from gases by a number of known methods. However, the simultaneous removal of carbon oxysulfide and carbon disulfide from gases is difficult.
It is generally known that adsorbents, such as active carbon, zeolites or silica gel, have only a very limited capacity for absorbing carbon oxysulfide and carbon disulfide. Gas purification processes such as washing with liquid basic media, involve considerable effort because the solubility of carbon oxysulfide and carbon disulfide in those media is minimal. In addition, working up of the spent solutions involves environmental problems.
There has been some acceptance of processes in which carbon oxysulfide and carbon disulfide are converted into hydrogen sulfide on solid media (generally zeolites, aluminum oxide and the like) and the hydrogen sulfide is subsequently removed from the gas mixture by known methods. The disadvantage of these processes lies in their high energy consumption. The conversion of carbon oxysulfide or carbon disulfide only takes place at high temperatures, generally on the order of 400 to 800.degree. C.
The process for converting carbon oxysulfide present in gases which is disclosed in DE-A-1 667 590 uses certain heavy metal oxides as catalysts on active carbon as support. The conversion reaction takes place at temperatures &gt;20.degree. C. The abrasion of the carbon and its combustibility make this process disadvantageous.
DE-A-220 394 discloses that aluminum oxide containing molybdenum, iron, tungsten, nickel or cobalt or certain combinations of these metals can be used as a catalyst for the reaction of carbon oxysulfide with steam. The metals are generally used in the form of sulfides. However, the hydrolytic reaction of carbon oxysulfide and carbon disulfide requires uneconomically high temperatures of 250 to 400.degree. C.